Organism large enough to see by naked eye.

A tissue barrier capable of keeping some substances out and letting others in.

Organism requiring magnification for observation.

An instrument permitting magnification of organisms too small to see clearly with the naked eye.

A naturally occurring substance found on the earth which is neither animal nor plant. Minerals have distinct properties such as color, hardness, or texture.

Soil that is mainly mineral material and low in organic material. Its bulk density is greater than organic soil.

A downy or furry growth on the surface of organic matter, caused by fungi, especially in the presence of dampness or decay.

The smallest particle of an element or compound that can exist by itself. Two atoms of oxygen make up a molecule of oxygen. Two atoms of oxygen and one atom of carbon make up a molecule of carbon dioxide.

A watery secretion, often thick and slippery, produced by gland cells. One function is to keep membranes moist.